1. Field of the Invention
The present invention relates to a touch panel, and more particularly, to a flat display panel with touch control function.
2. Description of the Prior Art
Currently, in the market of various kinds of consumer electronic products, touch panels have been widely applied in portable electronic devices such as personal digital assistants (PDA), mobile Phones, and notebooks for serving as the interface of information communication tool between the users and the electronic devices. Since modern electronic products increasingly become smaller, thinner, and lighter, the display with a touch panel has gradually become the key component of various electronic products in order to save space and to replace traditional input apparatuses, such as operation buttons, keyboard, and mouse, leaning on the trend of requirement of human-based designed flat computer.
A conventional touch panel is an individual touch control device, which may be fixed on the surface of a display panel or a display device. The conventional touch panel commonly has a conductive glass substrate, a conductive film disposed on the conductive glass substrate, and a plurality of spacers positioned between the conductive glass substrate and the conductive film. A transparent conductive layer is disposed on the opposite surfaces of the conductive glass substrate and the conductive film respectively, which may be electrically connected to a conductive wire and to an external control circuit through a flexible circuit board. According to the operation method of the conventional touch panel, when the user presses or touch the conductive film on the surface of the panel with his finger, the pressed point will have a voltage variation such that the location of the pressed point can be calculated in accordance with the quantity of voltage variation. Sequentially, an input signal representing the location of the pressed point can be transferred through the transparent conductive layer, conductive wire, and the flexible circuit board.
However, the above mentioned conventional touch panel is additionally attached on the display panel. Since the touch panel itself has a certain thickness, it reduces the light transparency and influence the light performance of the display device, and the combination of the display panel and the touch panel increases the total thickness of the display device. In addition, the conventional touch panel only supports the method of single touch for sensing the touch-generating input signal, which means only one pressed location or point can be sensed. Therefore, multi touch control is not accepted by the conventional touch panel, such that the application field of the conventional touch panel is restricted.
On another aspect, the manufacturers have developed to integrate the touch control function with the liquid crystal display (LCD) panel. Accordingly, when the surface of the liquid crystal display panel is being pressed, its upper glass substrate will be deformed so as to produce sensing signals. Generally, an LCD panel usually comprises a sealant or fiber spacers disposed in the periphery portion between the glass substrates in order to support the spacing or cell gap of the liquid crystal layer. However, the periphery portion of the glass substrates near the sealant is hard to be deformed because the sealant has a high rigidity. Accordingly, more power has to be provided for deforming the glass substrate when applying active force onto the glass substrate near the sealant in order to produce the sensing signal. For example, according to the operation of the conventional display panel having touch control function, probably an active force of only 20 grams is needed for pressing the central portion of the display panel to produce a sensing signal. However, when pressing the periphery portion of the display panel, an active force of more than 100 grams is needed for deforming the glass substrate near the periphery portion to produce the sensing signal, which is five times more than the active force of the central portion. In this situation, a user may feel that the sensitivity of the periphery portion is comparatively worse because only a big active force can produce the control signal in the periphery portion of the display, which is not convenient for use and also limits the function of the display panel.
As the above mentioned, since the conventional type of touch panel has disadvantages of raising the total thickness, lowering the lightness of the display device and un-uniform touch condition, the manufacturers of touch panel and display device have to research and develop new integrated products with properties of light, small, good sensitivity, and low fabrication cost.